1. Field of the Invention
The subject invention relates to a wireless power transfer system for powering or charging an electronic device or a battery, and more specifically, to a wireless power transfer system for a vehicle having a controller and a remote primary coil for inductively charging a secondary coil in an electronic device.
2. Description of the Prior Art
Mobile or portable electronic devices are increasingly being used for communication, entertainment and time management. These mobile electronic devices, such as mobile phones, personal data assistants, music players, cameras, GPS units, and other audio/video or communication devices, are carried by users during the course of daily activities, and as such devices are powered by batteries, the users must continually monitor battery life and anticipate when the batteries need to be charged, so that the devices do not inconveniently become inoperable due to a low battery condition.
Charging portable electronic devices currently requires the use of a charging cord having a connector connected to a power source. It is difficult for users to anticipate when they will be near a power source for a sufficient time period to charge the battery within the device. In a vehicle, the power source is typically a charging outlet such as a cigarette lighter. If the user charges the device in a vehicle, the user connects a special charging cord to the power outlet and the device, Charging cords typically include a unique connector arrangement for each type of device or each manufacturer. For example, an electronic device such as a cell phone is not likely to have the same connector arrangement as a portable compact disc player and a cell phone by one manufacturer typically will not have the same connector arrangement as a cell phone by a different manufacturer.
One resolution to the cumbersome use of such charging cords has been the introduction of electromagnetic induction technology; however manufacturers of vehicles have been slow to adopt such technology. Induction technology is employed in a wide range of applications, such as power transfer interfaces for electric vehicles, recharging electric toothbrushes, and powering smart-tags and security tags. However, all these devices use very special units for the primary and secondary coils that provide specific interface and relative location arrangements. Due to the difficulty in arranging specific interfaces within a vehicle, the inventors are not aware of any inductive charging systems currently being used in production vehicles for powering or charging a device.
Electromagnetic induction technology includes the use of a primary controller connected to a power supply and a primary coil that generates an electromagnetic field when a current flows through the coil. A secondary coil is provided in a remote electronic device such that when the device is placed in proximity to the primary controller, the electromagnetic field generated by the coil induces a current in the secondary coil of the remote electronic device. As such, the power is transferred wirelessly between the primary controller and the remote electronic device without the need for cumbersome charging cords.
Wireless power transfer systems eliminate the need to have open electrical contacts; however, the electromagnetic fields generated by such systems are relatively small. For this reason, secondary devices must be placed accurately into an electromagnetic field such that the primary coil in the wireless charger and the secondary coil in the electronic device are in a predefined relative position. As a result, chargers are still only being primarily designed for a specific make and model of electronic device so that the coils may be properly aligned, such as a battery powered toothbrush that comes with its own charging holder. There remains a continual need for chargers which generate electromagnetic fields that induce stronger currents in the secondary coils of electronic devices and which also provide for positioning of the secondary coil of the electronic device in a predefined relative position.